An inkjet-type recording head as one example of micro electro mechanical systems (MEMS) devices includes a passage-forming substrate in which pressure generating chambers communicating with nozzles for ejection of liquid droplets are formed, piezoelectric elements provided on one surface side of the passage-forming substrate, and a driver circuit substrate joined to the piezoelectric element side of the passage-forming substrate and provided with a driver circuit to drive the piezoelectric elements. The inkjet-type recording head drives the piezoelectric elements with the driver circuit, thereby generates pressure changes in liquid contained in the pressure generating chambers, and ejects liquid droplets from the nozzles.
As such piezoelectric elements, there has been proposed an element in a thin-film shape, which is formed on the passage-forming substrate by film deposition and lithography. Use of such piezoelectric elements in a thin-film shape carries an advantage in that the piezoelectric elements can be mounted at high density, but, on the other hand, makes it difficult to electrically connect the piezoelectric elements mounted at high density to the driver circuit.
To address this, there has been proposed a configuration in which bumps are provided on the driver circuit substrate, a recessed portion is provided in an adhesive layer for bonding the driver circuit substrate and the passage-forming substrate together, and the driver circuit and piezoelectric elements are electrically connected to each other via the bumps in the recessed portion (For example, see PTLs 1 and 2, and others).
By using bumps for connecting the driver circuit and the piezoelectric elements as described above, the piezoelectric elements arranged at high density and the driver circuit can be connected to each other easily at low cost.